Re: wrapping synchronization in objects?

From:

Victor Bazarov <v.Abazarov@comAcast.net>

Newsgroups:

comp.lang.c++

Date:

Wed, 01 Apr 2009 12:09:58 -0400

Message-ID:

<gr03kn$5tn$1@news.datemas.de>

Gernot Frisch wrote:

is it possible (win32, *nix, only) to create a template class that
locks/unlocks a mutex every time the value of an object is used?

How do you define "used"?

Like:

template <typename T> class wrapper
{
public:
wrapper() :m_t() {}
wrapper(const T& t) :m_t(t) {}

You probably need to define the copy semantics too (the copy c-tor and
the copy assignment op).

   operator T() const
   {
      T t;
      lock();
      t=m_t;
      unlock();
      return t;
   }
   T operator = (const T& t)
   {
      lock();
      m_t = t;
      unlock();
      return t;

Isn't it customary to return '*this' from an assignment op?

   }
private:
   T m_t;
   void lock()const {/*EnterCricitcalSection...whatever*/}
   void unlock()const{/*LeaveCriticalSection...*/}
};

int main()
{
   wrapper<int> i = 13;

return i;
}

In your program, then, there would be locking while the expression in
'return' is evaluated, right?

Why are you asking? Is there a problem with the program (besides the
stuff I've mentioned)? Does it not compile? Why ask "whether it's
possible" when you could just try it, don't you have a compiler handy?

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask